Methods and apparatus for troubleshooting scaleable multislice imaging system

ABSTRACT

The present invention, in one form, is an imaging system which, in one embodiment, alters the configuration of a detector array and a data acquisition system to determine degraded component performance and generate fault isolation information. More specifically, by altering the configuration to include different combinations of detector array cells, interconnections, and one or more data acquisition channels, fault isolation information is generated.

BACKGROUND OF THE INVENTION

This invention relates generally to computed tomography (CT) imaging andmore particularly, to troubleshooting of an imaging system.

In at least one known CT system configuration, an x-ray source projectsa fan-shaped beam which is collimated to lie within an X-Y plane of aCartesian coordinate system and generally referred to as the “imagingplane”. The x-ray beam passes through the object being imaged, such as apatient. The beam, after being attenuated by the object, impinges uponan array of radiation detectors. The intensity of the attenuated beamradiation received at the detector array is dependent upon theattenuation of the x-ray beam by the object. Each detector element ofthe array produces a separate electrical signal that is a measurement ofthe beam attenuation at the detector location. The attenuationmeasurements from all the detectors are acquired separately to produce atransmission profile.

In known third generation CT systems, the x-ray source and the detectorarray are rotated with a gantry within the imaging plane and around theobject to be imaged so that the angle at which the x-ray beam intersectsthe object constantly changes. A group of x-ray attenuationmeasurements, i.e., projection data, from the detector array at onegantry angle is referred to as a “view”. A “scan” of the objectcomprises a set of views made at different gantry angles during onerevolution of the x-ray source and detector.

In an axial scan, the projection data is processed to construct an imagethat corresponds to a two dimensional slice taken through the object.One method for reconstructing an image from a set of projection data isreferred to in the art as the filtered back projection technique. Thisprocess converts that attenuation measurements from a scan into integerscalled “CT numbers” or “Hounsfield units”, which are used to control thebrightness of a corresponding pixel on a cathode ray tube display.

To reduce the total scan time, a “helical” scan may be performed. Toperform a “helical” scan, the patient is moved while the data for theprescribed number of slices is acquired. Such a system generates asingle helix from a one fan beam helical scan. The helix mapped out bythe fan beam yields projection data from which images in each prescribedslice may be reconstructed.

At least one known CT imaging system utilizes a detector array and adata acquisition system (DAS) for collecting image data. The detectorarray includes detector cells or channels that each produce an analogintensity signal which is representative of the x-ray energy impingedupon the cell. The analog signals are then supplied to the DAS forconversion to digital signals. The digital signals are then used toproduce image data. Image artifacts, with the potential for patientmis-diagnosis, can be produced by the degradation or failure ofindividual detector cells, the DAS, and detector to DASinterconnections. Detector cell degradation as measured by gainnon-linearity typically produces ring or band annoyance artifacts. Inaddition, failure of cells at the center of the detector results in aspot on the image, which could be interpreted as a tumor or lesion.Similarly, degradation and failure of the interconnections and DASimpact the image quality. As a result of the complexity of the imagingsystem troubleshooting of components may be time consuming anddifficult.

Accordingly, it is desirable to provide an imaging system which detectscomponent failure and provides fault isolation information. It wouldalso be desirable to provide such a system without increasing the costand complexity of the system.

BRIEF SUMMARY OF THE INVENTION

These and other objects may be attained in an imaging system which, inone embodiment, alters the configuration of a detector array and a dataacquisition system to determine degraded component performance andgenerate fault isolation information. The imaging system includes amultislice detector array having a plurality of detector cells, an x-raysource for radiating an x-ray beam toward the detector array, a dataacquisition system (DAS), and a computer.

By altering the configuration of the detector array and channelselection within the DAS, degraded components may be isolated forreplacement. More specifically, detector intensity data is generated andconverted by the DAS for a reference scan. If the scan data does notconform to reference data, the configuration of the detector array andDAS are altered and additional reference scans are performed to providefault isolation information. More specifically, by altering theconfiguration of the detector array to include different combinations ofcells, different detector intensity data are generated to identifydegraded detector performance. In addition, the DAS configuration isaltered so that the detector intensity data is converted by one or anynumber of DAS channels. By comparing the results of the differentcombinations, degraded interconnection and DAS performance is identifiedand fault isolation information is generated.

By utilizing the multislice detector array and the DAS, specificdegraded components are identified. In addition, the described systemreduces the time required to isolate a failure and produces repeatableresults without increasing the cost and complexity of the system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial view of a CT imaging system.

FIG. 2 is a block schematic diagram of the system illustrated in FIG. 1.

FIG. 3 is a perspective view of a CT system detector array.

FIG. 4 is a perspective view of a detector module.

FIG. 5 is a block diagram of a scaleable data acquisition system of theCT imaging system shown in FIG. 1.

FIG. 6 is a functional block diagram of the scaleable data acquisitionsystem shown in FIG. 5.

FIG. 7 is a perspective view of one embodiment of a detector moduleshown in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 and 2, a computed tomography (CT) imaging system 10is shown as including a gantry 12 representative of a “third generation”CT scanner. Gantry 12 has an x-ray source 14 that projects a beam ofx-rays 16 toward a detector array 18 on the opposite side of gantry 12.Detector array 18 is formed by detector elements, or cells 20 whichtogether sense the projected x-rays that pass through a medical patient22. Each detector element 20 produces an electrical signal thatrepresents the intensity of an impinging x-ray beam and hence theattenuation of the beam as it passes through patient 22. During a scanto acquire x-ray projection data, gantry 12 and the components mountedthereon rotate about a center of rotation 24.

Rotation of gantry 12 and the operation of x-ray source 14 are governedby a control mechanism 26 of CT system 10. Control mechanism 26 includesan x-ray controller 28 that provides power and timing signals to x-raysource 14 and a gantry motor controller 30 that controls the rotationalspeed and position of gantry 12. A scaleable data acquisition system(DAS) 32 in control mechanism 26 samples analog data from detectorelements 20 and converts the data to digital signals for subsequentprocessing. An image reconstructor 34 receives sampled and digitizedx-ray data from DAS 32 and performs high speed image reconstruction. Thereconstructed image is applied as an input to a computer 36 which storesthe image in a mass storage device 38.

Computer 36 also receives and supplies signals via a user interface, orgraphical user interface (GUI). Specifically, computer receives commandsand scanning parameters from an operator via console 40 that has akeyboard and a mouse (not shown). An associated cathode ray tube display42 allows the operator to observe the reconstructed image and other datafrom computer 36. The operator supplied commands and parameters are usedby computer 36 to provide control signals and information to x-raycontroller 28, gantry motor controller 30, DAS 32, and table motorcontroller 44.

As shown in FIGS. 3 and 4, detector array 18 includes a plurality ofdetector modules 58. Each detector module 58 is secured to a detectorhousing 60. Each module 58 includes a multidimensional scintillatorarray 62 and a high density semiconductor array (not visible). A postpatient collimator (not shown) is positioned over and adjacentscintillator array 62 to collimate x-ray beams before such beams impingeupon scintillator array 62. Scintillator array 62 includes a pluralityof scintillation elements arranged in an array, and the semiconductorarray includes a plurality of photodiodes (not visible) arranged in anidentical array. The photodiodes are deposited, or formed on a substrate64, and scintillator array 62 is positioned over and secured tosubstrate 64.

Detector module 58 also includes a switch apparatus 66 electricallycoupled to a decoder 68. Switch apparatus 66 is a multidimensionalsemiconductor switch array of similar size as the photodiode array. Inone embodiment, switch apparatus 66 includes an array of field effecttransistors (not shown) with each field effect transistor (FET) havingan input, an output, and a control line (not shown). Switch apparatus 66is coupled between the photodiode array and DAS 32. Particularly, eachswitch apparatus FET input is electrically connected to a photodiodearray output and each switch apparatus FET output is electricallyconnected to DAS 32, for example, using flexible electrical cable 70.

Decoder 68 controls the operation of switch apparatus 66 to enable,disable, or combine the outputs of the photodiode array in accordancewith a desired number of slices and slice resolutions for each slice.Decoder 68, in one embodiment, is a decoder chip or a FET controller asknown in the art. Decoder 68 includes a plurality of output and controllines coupled to switch apparatus 66 and computer 36. Particularly, thedecoder outputs are electrically connected to the switch apparatuscontrol lines to enable switch apparatus 66 to transmit the proper datafrom the switch apparatus inputs to the switch apparatus outputs. Thedecoder control lines are electrically connected to the switch apparatuscontrol lines and determine which of the decoder outputs will beenabled. Utilizing decoder 68, specific FETs within switch apparatus 66are enabled, disable, or combined so that specific outputs of thephotodiode array are electrically connected to CT system DAS 32. In oneembodiment defined as a system diagnostic mode, decoder 68 enablesswitch apparatus 66 so that all rows of the photodiode array areelectrically connected to DAS 32, resulting in 16 separate slices ofdata being sent to DAS 32. Of course, many other slice combinations arepossible.

In one specific embodiment, detector 18 includes fifty-seven detectormodules 58. The semiconductor array and scintillator array 62 each havean array size of 16×16. As a result, detector 18 has 16 rows and 912columns (16×57 modules), which enables 16 simultaneous slices of data tobe collected with each rotation of gantry 12. Of course, the presentinvention is not limited to any specific array size, and it iscontemplated that the array can be larger or smaller depending upon thespecific operator needs. Also, detector 18 may be operated in manydifferent slice thickness and number modes, e.g., one, two, and fourslice modes. For example, the FETs can be configured in the four slicemode, so that data is collected for four slices from one or more rows ofthe photodiode array. Depending upon the specific configuration of theFETs as defined by decoder control lines, various combinations ofoutputs of the photodiode array can be enabled, disabled, or combined sothat the slice thickness may, for example, be 1.25 mm, 2.5 mm, 3.75 mm,or 5 mm. Additional examples include a single slice mode including oneslice with slices ranging from 1.25 mm thick to 20 mm thick, and a twoslice mode including two slices with slices ranging from 1.25 mm thickto 10 mm thick. Additional modes beyond those described are possible.

FIG. 5 is a block diagram of scalable data acquisition system (SDAS orDAS) 32 which is easily reconfigured to be used with either single sliceor multi-slice CT detector systems. SDAS 32 can be reconfigured byadding or removing printed circuit boards to accommodate the number ofslices provided by x-ray detector 18. SDAS 32 is configured to convertthe low level electrical current signal, or intensity signals, fromx-ray detector 18 to digital values for image reconstruction, displayand archive. Single slice third generation, fan-beam CT systems havetraditionally contained 300 to 1000 detector cells in the Azimuthaldirection. SDAS 32 correspondingly is required to provide an anti-aliasfilter (not shown) for each cell prior to Analog to Digital Conversion(ADC). DAS cells are traditionally referred to as channels. Detectorcells can be ganged or paralleled to one DAS channel. The digital outputfrom DAS 32 is usually transmitted either in a serial or semi-serialfashion, as described below in more detail, to reduce the amount ofinterconnecting hardware. Analog current signals from detector 18 aresupplied to input channels (not shown) of SDAS 32 via shielded ribbon orflex cables (not shown). The cables are connected to SDAS 32 at a DASbackplane 102. DAS Converter boards 104 are also plugged into DASbackplane 102. This interconnection provides several advantages. First,backplane 102 enables ganging the detector cells on the outside edges ofthe fan beam. Second, backplane 102 allows a redistribution of thedetector cells to appropriate converter boards 104. Signals from morethan one slice are contained in the same flex cable. Each converterboard 104 only serves one slice since the reconfiguration of DAS 32 fromone multi-slice configuration to another or to the single sliceconfiguration requires only the removal or addition of converter boards104. Third, backplane 102 enables a blending or weaving of DAS channelsand detector cells near the end channels of a converter board 104.

Another aspect of the SDAS 32 is converter boards 104 which combine theanti-alias filter and ADC on the same board rather on separate boards.Having the filter and ADC on the same board 104 enables the modularityrequired for scalable DAS 42. The integrated filter-ADC function on thesame board also limits the possibility of electromagnetic and conductedinterference because of short electrical lead lengths.

FIG. 6 is a functional block diagram of SDAS 32. As explained above,SDAS 32 processes low level analog signals from detector 18 into digitaldata. Once in digital form, the signal is manipulated and transmitted tocomputer 36 for storage. Several signal adjustments can be made viacontrol registers contained on each converter board 104. For diagnosticpurposes, SDAS 32 is configured to enable and set a special analog testvoltage into the signal conditioning stage of the converter boards. Inone embodiment, the test voltage will be programmable in 16384 stepsbetween 0 and −3 volts. It is used in the diagnosis of the S-DASacquisition and signal processing chain. The analog test signal can beenabled to either the input of the pre-amplifiers, or to a special testinput channel. The firmware is further configured to set a I to 16multiplication factor with respect to the test voltage when it isenabled into the pre-amplifier stage. The Analog to Digital (A/D)Converter block converts each supplied analog voltage to a digital wordlinearly proportional to the input signal level. In one embodiment, theoutputs are read once per view and sent to computer 36.

In operation of system 10, the performance of certain components becomesreduced or de-graded so that it is necessary to identify and replacethese components. For example, over time, the gain of certain cells ofdetector array 18 may become reduced, requiring identification andreplacement of a detector array 18, or more specifically, detectormodule 58. Similarly, a channel or board 104 of DAS 32 may fail,requiring replacement of, for example, board 104. In addition, aninterconnection between detector 18 and DAS 32 may fail, requiringreplacement. In one embodiment, the configuration of system 10 isaltered to fault isolate degraded components. More specifically, byaltering the configuration of detector array 18 and DAS 32, a specificcomponent of array 18, DAS 32, and the detector to DAS interconnectionis identified as degraded so that component may be replaced, for exampleby a service technician.

More specifically and referring to FIG. 7, by utilizing row selection ofdetector array 18 and a series, or plurality of DAS channels andinterconnections, specific tests, or patterns may be generated to faultisolate array 18, DAS 32, and the detector to DAS interconnection.Particularly, prior to performing a scan, the configuration of detectorarray 18 and DAS 32 are determined. For example, as described above,detector array 18 is configured in a system diagnostic mode with eachslice being 1.25 mm and DAS 32 is configured to use a selected, ordefined board 104 to convert the detector intensity data or signals. Ascan is then performed so that detector intensity data is generated bydetector array 18. Depending on the configuration of detector array 18,more specifically, decoder 68 and the FETs of switch apparatus 66,detector intensity data is generated for at least one row of detectorcells. The detector intensity data is then electrically connected to DAS32 using selected detector/DAS interconnections, for example cable 70.DAS 32 then generates digital data from the detector intensity data.More specifically, the detector intensity data is electrically connectedto at least one defined, or selected board 104. The detector intensitydata is then converted to digital data by board 104 of DAS 32.

Utilizing reference digital data from a reference scan having a defineddetector array 18 configuration, x-ray source 14 voltage and current,and scan mode, the collected digital data may be compared to thereference digital data. Degraded component performance is determined bycomparing the digital data from the scan to the reference digital data.More specifically, if the collected digital data does not favorablycompare to, i.e., is equal to or within a defined tolerance of, thereference digital data, a degraded component is identified by faultisolation. In one embodiment, the reference scan may be a scan justcompleted, or a previously completed scan. A degraded component may beidentified by performing a series of scans and by altering theconfiguration of detector array 18 and DAS 32 between each scan.

The degraded component is fault isolated by altering the configurationof detector array 18, DAS 32 and the interconnections. Specifically,different combination of detector cells are combined, the data issupplied to DAS 32 by different combinations of interconnections, andthe detector intensity data is converted by different DAS boards 104.More specifically, unique intensity data patterns and combinations ofdetector cells are generated by detector array 18 by altering theconfiguration. Particularly, and as shown in Table 1, by enablingdifferent combinations of FETs of switching apparatus 66, the detectorintensity data is altered.

TABLE 1 FET FET FET FET Row Row Row Row 4 3 2 1 Mode 2A 1A 1B 2B Gnd GndGnd Gnd 4 × 1.25 mm D2 D1 D1 D2 Gnd Gnd Gnd −5.0 4 × 2.5 mm  D3 + D1 +D1 + D3 + D4 D2 D2 D4 Gnd Gnd −5.0 Gnd 4 × 3.75 mm D4 + D1 + D1 + D4 +D5 + D2 + D2 + D5 + D6 D3 D3 D6 Gnd Gnd −5.0 −5.0 4 × 5.0 mm D5 + D1 +D1 + D5 + D6 + D2 + D2 + D6 + D7 + D3 + D3 + D7 + D8 D4 D4 D8 Gnd −5.0Gnd Gnd Cal 1 D3 D2 D2 D3 Gnd −5.0 Gnd −5.0 Cal 2 D4 D3 D3 D4 Gnd −5.0−5.0 Gnd Cal 3 D5 D4 D4 D5 −5.0 −5.0 −5.0 −5.0 Cal 4 D6 D5 D5 D6 −5.0Gnd Gnd Gnd Cal 5 D7 D6 D6 D7 −5.0 Gnd Gnd −5.0 Cal 6 D8 D7 D7 D8 −5.0Gnd −5.0 Gnd Cal 7 D1 D8 D8 D1 Gnd Gnd −5.0 −5.0 Cal 8 float float floatfloat

Particularly, by enabling at least one FETs, at least one detector cellis identified to generate intensity data to be converted by DAS. Asecond pattern of detector data may be generated by enabling a differentgroup of FETs so that a different detector cell or more than onedetector cell is identified and outputs of the identified detector cellsare combined to generate the detector data.

The detector data for the identified detector cells is then converted byDAS. DAS 32 is configured so that a selected channel of at least oneboard 104 is used to convert the detector intensity data to digitaldata. If the digital data is not equal to or within the specifiedtolerance range, in addition to altering the configuration of detectorarray 18, the configuration of DAS may be altered to generate faultisolation information. Specifically, the detector intensity data fromdetector array 18 may be converted using one, or more than one channelof a board 104, or by more than one board 104. By comparing the digitaldata from the performed scan, or first digital data, to the referencedigital data, or second digital data, DAS 32 may be fault isolated. Morespecifically, by examining the digital data from the selected boards, aspecific portion of board 104 or DAS 32 may be determined to bedegraded. For example, if the detector intensity data is electricallyconnected to a group of four selected boards 104 and three of theselected boards 104 generate the proper digital data and the fourthselected board 104 generates incorrect digital data, the fault can beisolated to the fourth selected board 104 and the electrical connectionsfrom detector array 18 to the fourth selected board 104. To faultisolate between the electrical connections and the fourth board 104, DAS32 may be configured to electrically connect the same detector intensitydata to a group of selected channel of the fourth selected board 104.The group of selected channels may have one or more channels, forexample, four channels, including a first channel, a second channel, athird channel and a fourth channel. If the first, second and thirdchannels generate, or convert, the detector intensity data to thecorrect, or proper digital data, i.e., equal to the reference data, andthe fourth selected channel does not, the fourth selected channel isfault isolated. If all four of the selected channels generate digitaldata which does not equal the reference data, the fault is in theelectrical connection or the entire fourth selected board 104. Byaltering the configuration of detector array 18 and DAS 32 a series, ormatrix of tests are executed to complete the fault isolation. In oneembodiment, where all components are properly operating, the group offaulty components is empty, or contains zero components.

The matrix of defined tests along with the configuration of detectorarray 18 and DAS 32 may be stored as a fault isolation algorithm andstored in a memory of computer 36. Execution of the algorithm implementsthe tests described above and determines if the obtained results areequal to the expected or reference results. Use of the algorithmgenerates fault isolation information with little or no intervention bya service technician. In addition, the algorithm could be implemented asan expert system based on the configuration, test matrix, and faultisolation information.

The above described system utilizes the multislice detector array andthe DAS boards to isolate faults so that specific degraded componentsare identified. In addition, the described system reduces the timerequired to isolate a failure and produces repeatable results withoutincreasing the cost and complexity of the system.

From the preceding description of various embodiments of the presentinvention, it is evident that the objects of the invention are attained.Although the invention has been described and illustrated in detail, itis to be clearly understood that the same is intended by way ofillustration and example only and is not to be taken by way oflimitation. For example, the CT system described herein is a “thirdgeneration” system in which both the x-ray source and detector rotatewith the gantry. Many other CT systems including “fourth generation”systems wherein the detector is a full-ring stationary detector and onlythe x-ray source rotates with the gantry, may be used. Similarly, thesystems described may be used with any multislice system. In addition,the fault isolation algorithm may be stored in computer 36 or in aseparate host computer. Accordingly, the spirit and scope of theinvention are to be limited only by the terms of the appended claims.

What is claimed is:
 1. A method of troubleshooting an imaging system,the imaging system including an x-ray source for emitting an x-ray beam,a multislice detector, and a data acquisition system having a pluralityof channels, said method comprising the steps of: altering aconfiguration of interconnections between the detector and the dataacquisition system; performing a scan after said altering step;generating detector intensity data; generating digital data based on thedetector intensity data; comparing the digital data to reference datahaving a defined detector configuration; and identifying a faultycomponent based on the comparison, and wherein altering a configurationof interconnections between the detector and the data acquisition systemincludes electrically connecting the same intensity data to a pluralityof channels.
 2. A method in accordance with claim 1 wherein the imagingsystem comprises a computer, and the altering, comparing, andidentifying steps are performed automatically under control of thecomputer.
 3. A method in accordance with claim 2 wherein the multislicedetector comprises a plurality of detector modules, the identifiedfaulty component is a detector module, and further comprising the stepof replacing the faulty detector module.
 4. A method in accordance withclaim 2 wherein the data acquisition system comprises a plurality ofboards, the identified faulty component is a detector acquisition systemboard, and further comprising the step of replacing the faulty detectoracquisition system board.
 5. A method in accordance with claim 2 whereinthe identified faulty component is an interconnection between thedetector and the data acquisition system, and further comprising thestep of replacing the faulty interconnection.
 6. A method in accordancewith claim 1 wherein the detector array further comprises a plurality offield effect transistors, and wherein altering a configuration ofinterconnections between the detector and the data acquisition systemcomprises the step of enabling different groups of field effecttransistors.
 7. A method in accordance with claim 1 wherein altering aconfiguration of interconnections between the detector and the dataacquisition system comprises the step of combining groups of detectorcells to generate additional detector data.
 8. A method in accordancewith claim 1 wherein converting the detector intensity data to digitaldata comprises the steps of: converting the detector intensity data tofirst digital data using a first channel of the plurality of channels;and converting the detector intensity data to second digital data usinga second channel of the plurality of channels.
 9. A method in accordancewith claim 8 wherein identifying a faulty component further comprisesthe step of comparing the first digital data to the second digital data.10. An imaging system configured for troubleshooting, said imagingsystem comprising: a multislice detector array; a data acquisitionsystem including a plurality of channels; and an x-ray source configuredto emit an x-ray beam toward the multislice detector array, said dataacguisition system configured to acquire and process data from saidmultislice detector array; said imaging system configured to: alter aconfiguration of interconnections between said detector array and saiddata acquisition system channels by electrically connecting the sameintensity data to a plurality of channels; perform an x-ray scan afteraltering the configuration of interconnections; generate detectorintensity data based on the scan; generate digital data based on thedetector intensity data; compare the digital data to reference datahaving a defined detector configuration; and identify a faulty componentwithin said imaging system based on the comparison.
 11. Atroubleshooting system in accordance with claim 10 wherein the imagingsystem comprises a computer, and said troubleshooting system isconfigured to alter the configuration of interconnections between thedata acquisition system prior to performing the scan, compare theoriginal data to reference data having a defined detector configuration,and identify a fault component based on the comparison automaticallyunder control of the computer.
 12. A troubleshooting system inaccordance with claim 11 wherein the multislice detector comprises aplurality of detector modules and said troubleshooting system isconfigured to identify fault detector modules.
 13. A troubleshootingsystem in accordance with claim 11 wherein the data acquisition systemcomprises a plurality of boards and said troubleshooting system isconfigured to identify faulty detector acquisition system boards.
 14. Atroubleshooting system in accordance with claim 11 further comprising aplurality of interconnections between the detector and the dataacquisition system, and said troubleshooting system is configured toidentify faulty interconnections between the detector and the dataacquisition system.
 15. A troubleshooting system in accordance withclaim 10 wherein to convert the detector intensity data to digital data,said troubleshooting system is configured to: convert the detectorintensity data to first digital data using a first channel of saidplurality of channels; and convert the detector intensity data to seconddigital data using a second channel of said plurality of channels.
 16. Atroubleshooting system in accordance with claim 15 wherein to identify afaulty component, said troubleshooting system is further configured tocompare the first digital data to the second digital data.
 17. Atroubleshooting system in accordance with claim 12 wherein the detectorarray further comprises a plurality of field effect transistors, andwherein to alter a configuration of interconnections between thedetector and the data acquisition system, said troubleshooting system isconfigured to enable different groups of field effect transistors.
 18. Atroubleshooting system in accordance with claim 10 wherein to alter theconfiguration of interconnections between the detector and the dataacquisition system, said troubleshooting system is configured to combinegroups of detector cells to generate additional detector data.